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<b>let </b><font color="Maroon">c<sub>1</sub></font> be    <a href="subset_1.html#M1">Element</a> of  <a href="qc_lang1.html#K8">QC-WFF</a> ;<br/><b>let </b><font color="Maroon">c<sub>2</sub></font> be  non <a href="xboole_0.html#V1">empty</a> <a href="subset_1.html#NM2">Subset</a> of <a href="qc_lang1.html#K1">QC-variables</a> ;<br/>



<b>set </b><font color="Maroon">c<sub>3</sub></font> =  <a href="qc_lang1.html#K12">'not'</a> <font color="Maroon">c<sub>1</sub></font>;<br/>
<a NAME="E1:47"/><i><font color="Green">E26</font></i>: 
 <a href="qc_lang1.html#K12">'not'</a> <font color="Maroon">c<sub>1</sub></font> is <a href="qc_lang1.html#V3">negative</a>
 
<b>by </b><i><a class="ref" href="qc_lang1.html#D18">QC_LANG1:def 18</a></i>;<br/>
<a NAME="E2:47"/><b>then </b>
 <a href="qc_lang1.html#K17">the_argument_of</a> <span class="p1">(<span class="default"><a href="qc_lang1.html#K12">'not'</a> <font color="Maroon">c<sub>1</sub></font></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>1</sub></font>
 
<b>by </b><i><a class="ref" href="qc_lang1.html#D23">QC_LANG1:def 23</a></i>;<br/>
<b>hence </b><a NAME="E3:47"/>
 <a href="qc_lang3.html#K4" target="_self">Vars</a> <span class="p1">(<span class="default"><a href="qc_lang1.html#K12">'not'</a> <font color="Maroon">c<sub>1</sub></font></span>)</span>,<font color="Maroon">c<sub>2</sub></font> <a href="hidden.html#R1">=</a>  <a href="qc_lang3.html#K4" target="_self">Vars</a> <font color="Maroon">c<sub>1</sub></font>,<font color="Maroon">c<sub>2</sub></font>
 <b>by </b><i><a class="txt" href="qc_lang3.html#E1:47"><i><font color="Green">E26</font></i></a>, <a class="txt" href="qc_lang3.html#E49"><i><font color="Green">Lemma22</font></i></a></i>;<br/>


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